1. Field of the Invention
This invention relates to a clutch for linking a compressor with a drive means therefor.
2. Background of the Invention
Heavy vehicles, such as lorries, are normally fitted with a pneumatic braking unit and other pneumatically-controlled systems with air supplied by a compressor activated by the engine via a transmission, usually with gears, which maintains operating pressure in the pneumatic system or systems.
When there is no consumption of air, for example for braking, usually an automatic valve discharges any excess pressure in the system. Further savings in running can however be achieved by disengagement of the compressor when the pressure in the pneumatic system is equal to the maximum desired value and, reconnecting it as soon as its activation becomes necessary to restore the working pressure in the pneumatic system. In this way, there is a constant saving in fuel, since activation of the compressor, which takes power from the engine, only occurs for the time required to recharge it to compensate for the effective air consumption for braking, etc. without discharging the excess pressure to no purpose.
To this effect, compressors have been constructed which are fitted with a pneumatic disengagement clutch, but these constructions are complex and require substantial modifications to the structure of the compressor to contain the overall volume of space, which is high, and in addition induce considerable bending stresses on the compressor shaft itself and overload on its supports, produced by the necessary larger distance of application of radial thrust due to the drive gearing, which often requires over-dimensioning of the compressor shaft and its supports.